Conventional resistive memory devices can store data values by programming resistive memory elements between two different resistance states: a high resistance (Roff) and a low resistance (Ron). A memory element can be programmed from a high resistance to a low resistance by applying electrical conditions that create a programming voltage across the memory element, resulting in a programming current flowing through the memory element.
A conventional resistive element programming operation is shown in FIG. 15. FIG. 15 is a graph showing an element resistance (Relement) (on a logarithmic scale) versus a programming current (Iprog) (on a logarithmic scale) in a programming operation. The programming operation programs an element from a high resistance state to a low resistance state (shown by “Roff to Ron”).
In the conventional programming operation shown, a low resistance state (Ron) can correspond to a maximum current (Imax) allowed to flow through a memory element in the programming operation.
Conventionally, data values stored in resistive memory elements are determined with read operations. In a conventional read operation, a resistance of the memory elements is sensed. Typically, electrical conditions can be applied that cause a read current to flow through the memory elements being read.
A known problem with conventional resistive memory devices is “read disturb”. A read disturb occurs when a read operation (or number of read operations) cause a memory element that was in a high resistance state to unexpectedly change to a low resistance state, thus creating an erroneous data value.